Hindustan Petroleum Corporation [HPCL] — Delivery Charges

Address:

Bangalore, Karnataka

I booked a refill for a cylinder and the delivery boy asked me for Rs 570 for cylinder which was priced Rs 540 (As per Bill) I asked the reason for extra then he said everyone has to give that amount. I understand sometimes we tend to pay little extra as a tip (Being generous) but asking for extra amount which is fixed doesnt make any sense. He asked me to give the amount and wasnt ready even to leave without that.
So the question is-
Is delivery charge included in the price?
If not then is there a fixed price?
30 is not a big amount but asking for any fixed amount inflates the charges of any product which is not good at all.